Crews from Asplundh Tree Expert Co. work on expanding CMP's power line corridor near Merrill Road in Lewiston in 2011. The Maine Public Utilities order that authorized the expansion also directed CMP on taking trees outside its rights of way for all power-line corridors in Maine.

HALLOWELL — Maine has maple, elm, hemlock, pine and spruce, to name a few. But add to the many varieties of trees two other distinct characteristics: “hazard” trees and “danger” trees. Each presents potential harm to Maine’s power lines, and to Mainers’ access to electricity.

To limit that harm, and to protect landowners’ property, a pending agreement between the Maine Public Utilities Commission and Central Maine Power Co. will — if signed — make it clear CMP cannot cut trees outside the company’s rights of way along power lines without prior landowner agreement.

The definitions were refined during a two-hour meeting on Nov. 13 between CMP, Maine’s largest power transmission company, and the state regulatory agency, which oversees public utilities. The public can comment on the new definitions until Nov. 30.

Sometime after that, likely in December or January, the Maine PUC will vote to determine whether CMP has satisfied the commission with its new definitions, said Paulina Collins, a spokeswoman for the Maine PUC.

Despite the new agreement, CMP spokesman John Carroll said the company is still wary it could be held liable and even fined, under federal law, for power outages caused by downed trees — even trees outside CMP’s jurisdiction.

“We still have a certain level of anxiety,” Carroll said. “We think this could create situations that we may in the future not be making the right, appropriate efforts to comply with federal standards. We’ve made an argument, the commission has just disagreed and we are just moving on.”

That federal law, the U.S. Energy Policy Act of 2005 came in the wake of one of the country’s worst blackouts in 2003, in which some 50 million people in the eastern United States lost power. That outage, the result of a cascading series of events, was ultimately blamed on a downed tree.

Maine was not affected by that outage, but the new federal law affects Maine as part of a an effort to ensure reliability nationwide.

The law also established the National Electric Reliability Council and put more responsibility for trees on transmission companies like CMP. Under the law, they can be held liable for major, avoidable outages and fined based on their impacts.

Carroll said that’s what’s troubling for CMP, but going forward it will document the danger and hazard trees it cannot obtain permission to remove, in hopes it will provide the company some protection.

The new agreement between CMP and the PUC stems from a June 2008 order that authorized the construction of CMP’s more than $1 billion power transmission system upgrade, known as the Maine Power Reliability Program.

The ongoing project stretches from Eliot in southern Maine to Orrington near Bangor and involves major power-line improved reliability and adding new transmission lines.

Earlier this year, the PUC determined that CMP’s working definitions for hazard and danger trees and how they would be removed did not appear to be in compliance with its June 2008 order permitting the power corridor expansion.

In August 2012, the PUC ordered CMP to become compliant with the June 2008 ruling, which in essence said any trees not on CMP property and outside of the company’s rights of way could not be removed or pruned without the tree owner’s permission.

Both the PUC and CMP said the language change was meant to protect landowner rights going forward.

Under its operation manuals, CMP appeared to reserve the right to cut trees outside its rights of way if those trees posed the potential of falling onto power lines, creating a danger for line workers or disrupting the power supply lines.

In some places along the route, including in Lewiston, CMP worked with landowners and local officials to either reroute its proposed power corridor or to employ “engineered” solutions, including 140-foot-tall transmission towers that would carry the power lines above trees. In Lewiston the cost of this was accommodated by a tax-increment financing program offered to CMP by the city.

Carroll said numerous stipulations, from a variety of people and interests groups, were negotiated into the original agreement that set up the Maine Power Reliability Program. Those stipulations covered everything from setting up pilot projects for all-electric vehicles to how trees and other vegetation outside CMP’s power corridor could be managed.

The trees that pose the most concern for CMP are those outside the rights of way but tall enough to land on a power line if they were to come down. For example, a tree 60 feet from the right-of-way boundary that’s 100 feet tall could still fall onto the line. If that tree is dead or dying or otherwise in a condition that presents a danger in normal weather conditions, it would be identified as a hazard tree.

Other healthy trees that under normal weather conditions do not pose any threat are considered danger trees, simply because they could, in the right conditions, fall and damage the transmission lines and interrupt service.

Under the new definition, those trees would not necessarily be candidates to be cut down, Carroll said.

There has to be some rationale for removing the tree, he said, for example, if it’s a lone pine more susceptible to wind damage or a species of tree that doesn’t live long or is known to be damaged or diseased.

“What this agreement does is it sort of formalizes that if we do not have those rights already written into our agreement with a landowner, then we will then approach the landowner for rights to cut that down,” Carroll said.

He said many landowner agreements contain provisions that allow CMP to remove hazard and danger trees on land adjacent to the transmission corridors. Sometimes, those provisions are written into deeds and come with a property, and new landowners are not always aware of them, which can be another point of friction.

According to a Nov. 19 letter to the PUC from CMP’s attorneys, going forward the company “will not remove any danger trees that appear healthy and are located on the edge or outside of its right-of-way and do not pose an obvious or immediate threat to CMP’s facilities under normal weather conditions, unless the landowner consents to the removal of such trees.”

That letter, by Portland-based lawyer Jared des Rosiers notes that CMP is already party to some existing easement agreements that grant the company the right to remove danger trees on property outside the identified right-of-way, but even those trees will not be cut without specific landowner permission.

“Instead, CMP will seek the landowner’s written consent to remove such trees in accordance with the process outlined in its September 24, 2012, compliance filing,” des Rosiers wrote. “Going forward, CMP where possible will seek new easement rights that give the utility the right to remove danger trees outside of the right-of-way . . . CMP intends to rely on those rights in the future to establish the landowner’s consent to the removal of danger trees on the edge or outside of the right-of-way.”